I've attached some pics to compare the size and show the device.
1st) Gamevice and Nintendo Switch
While the Gamevice is a little wider, the beveled sides help keep it comfortable.
2nd) Gamevice, Switch, JXD S192 (top), 3DS, Vita, GPD XD
This was to give contrast to the other devices, and their controls. It also compares size.
4th) Gamevice, Switch, JXD S192 (Left) Cube Mix Plus w/iPega PG-9023 (Right)
I wanted to show how big some devices can get, just to play games. I prefer the Cube Mix Plus to the GPD Win any and every day though.